Apparatus for straightening and for relieving stresses in workpieces



July 14, 1959 G. H. APPEL 2,894,421 APPARATUS FOR STRAIGHTENING AND FOR RELIEVING STRESSES IN WORKPIECES Filed Jan. 12, 1956 4 Sheets-Sheet 1 ULI INVENTOR.

GERHARD H. APPEL ATTORN-EYS July 14, 1959' G. H. APPEL 2,894,421

APPARATUS FOR STRAIGHTENING AND FOR RELIEVING STRESSES IN WORKPIEICES Filed Jan. 12, 1956 4 Sheets-Sheet 3 REVERSE INVENTOR.

By GERHARD H. APPEL ATTORNEYS DRAIN July 14, 1959 (5.1-4. APPEL APPARATUS FOR STRAIGHTENING AND FOR RELIEIVING STRESSES IN WORKPIECES 4 Sheets-Sheet 4 Filed Jan. 12, 1956 INVENTOR.

GERHARD l'l APPEL M'WV ATTORNEYS United States Patent APPARATUS FOR STRAIGHTENING AND FOR RELIEVING STRESSES IN WORKPIECES Gerhard H. =Appel, Toronto, Ontario, Canada *Application January 12, 1956, Serial No. 558,750 3 Claims. (Cl. 78-14) This application directed to apparatus is a parent of my copending application Ser. No. 627,446 directed to method.

The inventionrelates to a new apparatus for relieving longitudinal stresses in elongated workpieces 'by cold forging.

Anelongated workpiece is fed axially andintermittently in small increments through: the throat of an annular set of hammers or forging dies. The workpiece is'held at its trailing and leading ends in axial alignment with the throat of the dies. These impart, in off-beat relation to the feed, aseries. of sharp rapidly delivered hammer blows which reduce the increments to a plastic condition and thus relieve them of longitudinal stresses. With the leading end held and guided to travel axially of the die throat, the leading end, already plasticized and relieved of longitudinal stress, is not again subject to such stress. v

Since the line connecting the. engaged points ofthe workpiece, namely the leading end, and the part in the die throat, is a straight line, the workpiece will also be straightened. v

Objects and advantages of the invention will become apparent from the following .detailed description of the method and a preferred form of the apparatus for carrying it out as illustrated in the accompanying drawings.

In these drawings:

- Fig. 1 is a diagrammatic small scale topplan view'of the machine as a whole showing the relation of the forming head, with the feed means to the right of..-the head, and the workpiece receiving-meansto theleft of the head; V p

V Fig. 2 is a diagrammatic exploded view of theforming apparatus of the machine, partly vin section on line 22' of Fig. 1;

Fig. 3 diagrammatically shows .the feeding means: in relation to the forming means;

Fig. 4 is a fragmentary view of a part; Fig.5 is a longitudinal plan view, partly in section, of theworkpiece receiving means. t

Referring to the drawings, the apparatus shown is adapted to carry out the new straightening .and stress relieving method in cooperation with a cold forging machine of the type disclosed in the copending Appel application, Serial No. 732,866, .filed May 5, 1958 and application, Serial No. 450,500, filed August 17, 1954. It will be appreciated, however, that the methodcan be carried out in cooperation with other types of forging or swaging machines. Insofar as it concerns the present invention, the machine comprises .a continuously revolving motor having a clutch, not shown, whereby it may be connected to a pinion 16 meshing with a ring gear 18, in turn'me'shing'with four pinions 20 mounted on four shafts 22 (Figs. 2 and v4). Each shaft 22 mounts two eccentrics 2426 (Fig. 4) displaced relatively 80.; The eight eccentrics are operatively, connectedto eight rings 2825f eight driver rods 30 (Fig.';2).

2,894,421 Patented July 14, 1959 Thus, when the motor clutch is engaged, the parts 16-18-20-22--2426 will revolve and because of the eccentricity of parts 24-26 and their connection to the rings 28 of the rods 30, the rods 30 will continuously reciprocate. These eight rods cause forming strokes of dies operated thereby to take place in properly timed relation to the rotation of the four shafts 22 and their eight eccentrics 24 and 26.

The eight driver rods 30, as they continuously reciprocate, slide their cams 32 between rollers 34 and 36. Rollers 34 are backed by fixed structure or the frame 38 of the machine.

Rollers 36 are between the cams 32 and die movers 40 in turn separated by springs 42 from dies 44 arranged radially around a workpiece 46 (Figs. 2 and 3).

Reciprocation of the rods 30* operating through their earns 32 and the rollers 36 and with reactions backed bythe rollers 34 and the fixed structure 38 and operating on parts 40 causes the dies 44 to move radially towards the workpiece 46 in forming strokes.

The foregoing is all clearly and more in detail described in a copending application 450,500 and the disclosure of that application is incorporated hereinto by reference to the extent that it is necessary to understand more than has heretofore been given of the forming operation. For the purposes of the present application, it is believed suflicient to say that the apparatus which causes the forming is shown herein only enough to relate it to the feeding and the stress relieving means which combine with the forming means to produce the machine and method of the-present application. Further details of the forming operation can be obtained by reference to application Ser. No. 450,500.

It' is sufficient to say that the forming operation causes a plasticizing of the increment of the workpiece that happens to be within the throat of the radially moving dies and because of such plasticizing, that increment is relieved of'stresses.

A pump 48 supplies fluid under pressure to a feed means which is constructed to provide intermittent incremental forward feeding and blocking of the workpiece, and also retraction or reverse. Thus, the workpiece is moved forward in small increments and comes to rest between increments of feed and when in rest the workpieceis held immovable against reactions. caused thereon by the forming strokes, which by means (Fig. 4) later to be'described is properly timed in relation to the feeding strokes so as to create the off-beat relationship that will later be described more in detail, it being understood that this term is simply a convenient expression for describing a forming and feeding relation wherein the workpiece is fed incrementally in short intermittent strokes and comes to rest between feed strokes and while at rest is formed in forming strokes which are spaced apart by the feeding strokes so that alternate feeding v and rest-forming strokes take place.

The operation of the feeding means is initiated by the Pressure from line 54 is now available to lines 5658.v

Such pressure in line 56 causes movement of the piston 60 of valve 62 to the left to close oif lines 64, 66, and 68.-

A transversely bored rotor of valve 72 mounted onbne' of the eccentric shafts 22 (Fig. 4) opens and of cylinder 76"containing a differential area piston 78 olosesline 58 periodically in properly timed relation to themovement of the forming dies 44 and controls the supply of pressure fromlines 5458 to the rear part 74 whose rod 80 is connected to the workpiece 46 in a manner later to be described. Between valve 72 and cylinder 76 is a one-way pressure valve 82 which opens by the pressure in line 58 when valve 72 is open to establish pressure on the rear of piston 78 for forward feeding. A short forward feed stroke then takes place and due to the control established on valve 72 by the forming eccentric shaft 22, valve 72 immediately closes and in so doing causes valve 82 to close and establish a block in line 58 and cylinder 76 to maintain the piston 78 immovable against reaction thereon from the left due .to the forming of the workpiece 46 connected to piston rod 80, to hold the piston 78, its rod 80 and the workpiece immovable during the forming stroke. On the next opening of valves 7282, pressure is once more supplied to cylinder part 74 for forward feeding of the piston 78, its rod 80 and the workpiece.

The foregoing results are due in part to the fact that the piston 78which divides cylinder 76 into a rear part 74 and a forward part 84 is of differential area with its rear face at part 74 exceeding in area that of the forward face exposed to cylinder part 84. A line 85 connects cylinder part 84 to line 58 between valves 72 and 82.

All of the foregoing is more in detail described in a copending application Ser. No. 561,466 relating to feed means particularly and in interest of brevity the description of feed means will be abbreviated, but it is understood that the disclosure of application Ser. No. 561,466 is incorporated hereinto by reference in order to provide a more full understanding of the feed means.

When the operator wishes to terminate feed and retract the workpiece, he causes the barrel piston 50 of valve 52 to move to the right which closes off lines 56 and 58 and valves 7282 and terminates the forward feeding. Line 68-will open to move the piston 60 of valve 62 to the right to open line 64 to pressure and also to open line 66 to the drain valve 86 in line 88 which opens automatically due to the pressure in line 66. With valve 86 open, cylinder part 74 will be open to drain 89 through lines 66-86.

This movement of piston 50 of valve 52 and the corresponding movement of the piston 60 of valve 62 and the functioning just described operates to move piston 78 rearwardly for reverse feeding, but since reverse feeding forms no part of the present invention, nothing further will be said about it here, but it is understood that a full explanation of reverse feeding using the means herein shown may be obtained by reference to the copending application Ser. No. 561,466 whose disclosure is incorporated into this application by reference for the purposes of fully describing and disclosing forward as well as reverse feeding, and also blocking between forward feed steps.

Piston rod 80 which is under the control of the feed means previously described is operatively connected to a chuck 90 mounted in a head 92 (Figs 1, in turn mounted to slide on the tie rods 94 of stationary structure 38 of the forming machine.

Thus, forward movement of the piston 78 and rod 80 causes forward movement of the head 92 and the chuck 90' for workpiece feeding.

The chuck 90 also supports a mandrel rod 96 upon which is a mandrel 98 disposed inside the throat 100 of the dies 44, as well as supporting the workpiece 46 in the throat 100 of the dies 44.

The machine thus far described and the parts thus far enumerated have been previously described in my copending applications, Ser. No. 450,500 and Ser. No. 561,466 and these parts, except in combination with the parts about to be described specifically and per se, form no part of the present invention. However, they have been described in detail here, but more in detail in the said applications, because they combine with the parts to be described hereafter to form the novel machine of the present invention-a machine which operates for forming and feeding in off-beat relation.

In straightening and relieving longitudinal stresses in accordance with the improved method, the leading end of the workpiece as it emerges from the die set is firmly engaged and rigidly held in coaxial alinement with the die set. It is also desirable although not essential to the attainment of the desired result, that the end of the workpiece supported by the chuck be precisely alined with the die set. Any tendency of the workpiece to elongate more at one side than the other and thus to bend or twist transaxially is counteracted by the action of the die elements which plasticized the material and forces it into precise axial alinement with the support at the reduced end of the workpiece. This, of course, develops longitudinal stresses along the entire length of the workpiece but those stresses are completely relieved when the material becomes plastic under the dies. Thus, the compensation for the conditions which produce the tendency to bend is effected within the area where the metal is temporarily in a plastic condition and therefore the redistribution ofmetal' required for the production of a straight workpiece is effected without the development of any stresses in the workpiece. In the case of tubular workpieces, this redistribution of metal results in substantial equalization'of the wall thickness throughout the entire length of the workpiece. Accordingly, by use of the new method, a straight, stress-free workpiece and therefore a'better product is produced in a single operation and with material saving in production costs.

Workpiece receiving It will be understood that the forming operation provided by the parts previously described operates to plasticize that small increment of the long workpiece 46 which is within the throat of dies 44. Now, that increment being there plasticized in accordance with my forming method and by my forming means is there and then straightened and relieved of longitudinal stresses.

The first such increment, at the leading end of the workpiece which is the first increment to be formed, as it emerges from the die throat 100 is firmly engaged and rigidly supported and held in coaxial alignment with the die throat by means now to be described. It also happens that the read end of the workpiece is supported by the chuck 90 and is thus also precisely aligned with the die throat. Therefore, any tendency of the workpiece to elongate more at one side than the other and thus to bend or twist transaxially is counteracted by the action of the dies which plasticize the material and force it to precise axial alignment with the die throat and the support at the leading end of the workpiece; likewise, any'longitudinal' stresses along the length of the workpiece are completely relieved'in the increment plasticized in the die throat.

When the dies plasticize aworkpiece of non-uniform section measured around the axis, the part in the dies of larger section tends to 'bedisplaced transaxially or circumferentially towards the smaller section, thus balancing or equalizing the metal volume around the axis, in the plasticized area, and thus reducing variations in dimension relative to the axis. The phenomenon is especially manifested in thecase of tubular workpieces. This causes a substantial relief of the longitudinal stresses in the workpiece.

The invention, therefore, contemplates and the application-shows the provisionof means for receiving and supporting the very first increment of the workpiece immediately uponits emergence from the die throat.

The support herein disclosed (Fig. 5) is in the form of a piston reciprocal in a cylinder 111 mounted adjacent the discharge. side of the die throat and coaxially aligned with it. The piston 110 includes a cup shaped shell 112 closed at its tea-rend bya plug 113. A socket 114 is shaped and dimensioned to receive the end of the workpiece, that is the leading increment as it emerges from the dies, with a tight gripping fit and this socket 114 is central of the plug 113. V

In the particular machine illustrated a cylinder 111 is rotatably supported within a tubular liner 115 as by bearings 116. The liner is fitted into a rigid sleeve member 117 suitably secured to the frame structure of the machine. As herein shown, the sleeve is seated in an aperture 118 in the frame member and is formed with a flange 119 adapted to abut the inner wall of the frame member and hold the sleeve against the axial movement. In this instance the sleeve also provides support for the die set which is mounted on and secured to the forward end of the sleeve in any suitable manner.

The cylinder is secured against the endwise movement relative to the liner by a collar element 120 which permits rotation of the cylinder with the piston and the workpiece supported thereby. A port 121 in the sleeve and liner provides for admission of fiuid coolant to the space between the cylinder and the liner, the coolant being discharged through a port 121 in the collar 120. Pressure fluid such as compressed air is admitted to the aft end of the cylinder by way of a port 122 in the end wall of the cylinder. Thus, by directing compressed air through the port 122, the piston may be driven toward the forward end of the cylinder to impose a yieldable resistance to the advancing workpiece through the die set.

At the beginning of a forging operation, compressed air admitted to the cylinder through the port 122 holds the piston at the forward end of the cylinder closely adjacent the die set. The workpiece therefore enters the socket 114 immediately on emerging from the forging dies. A substantial pressure as, for example, 50 p.s.i., is maintained in the cylinder as the forging operation proceeds, thus applying a yielding force to the piston counter to the feed of the workpiece. This effectually keeps the workpiece firmly seated in the socket and therefore coaxially alined with the die set through its entire length. The piston is forced back into the cylinder as the workpiece advances through the die set.

To facilitate disengagement of the workpiece from the socket 114 the piston is provided with a pressure actuated plunger 123 adapted to be projected into the socket 114 from its inner end. The plunger 123 as shown is formed with a cylindrical head 124 extending through an opening at the end wall of the piston. A flange 125 adjacent the forward end of the head limits rearward movement of the plunger.

Upon completion of the forging operation the head 92 and chuck 90 are retracted in the usual manner with the dies preferably opened up to afford clearance for withdrawal of the work. The support piston 110, being subjected to the pressure in the cylinder, moves along with the work until it reaches the end of the cylinder. The pressure on the head 124 then acts to advance the plunger 123 and push the workpiece from the socket. Upon its withdrawal from the die set, the workpiece may be released from the chuck and removed from the machine.

It will be apparent from the foregoing that the novel straightening and stress relieving method provided by the invention materially improves the product produced by cold forging and swaging operations. The finished workpiece produced by this method is precisely straight and completely free of bending stresses. In the case of tubular workpieces, the walls are more nearly of uniform thickness. Furthermore, production costs are reduced since a number of supplementary operations heretofore required are eliminated. While the new method can be carried out in various ways and with different types of equipment, the invention provides simple and efiicient apparatus for that purpose which is easy to operate and 6 which is readily applicable to conventional cold forging or swaging machines.

It will be observed that there has here been disclosed an apparatus or combination wherein the basic element is an off-beat plasticizing means, namely, the dies 44 and the parts for relatively moving the workpiece and the dies in the olf-beat relation previously mentioned, with the combination including the guide or socket 114 which receives and holds and guides the plasticized leading increment of the workpiece coaxial with the travel of that increment through the throat of the dies and the travel of the next increments also through that throat. Thus, the leading increment of the workpiece which is plasticized and thus destressed in the throat is held against being stressed thereafter during plasticizing of the next increment.

The increments are plasticized while stationary and then moved longitudinally but the longitudinal movement is at a moment when the workpiece increment is free of the dies. Thus, an increment once plasticized is no longer subject to forces orstresses.

The leading increment once plasticized is immediately received in the support 114 and held thereafter so as to move only in a path aligned with the throat of the dies.

The socket 114 functions as more than merely a guide for a workpiece. It functions to receive the destressed leading increment immediately after that increment is plasticized and to support and guide that increment and thus, all the succeeding increments, in a properly guided path which insures the entire workpiece, made up of many increments, being destressed and straight and properly dimensioned.

It will be observed that the dies are arranged radially and oppositely to provide a workpiece girdling and receiving throat; that the feeding means causes the workpiece to be fed intermittently and axially through the throat of the dies; that the forming means causes the dies to move intermittently, simultaneously and oppositely and radially inward toward the axis of the throat and to plasticize the increment of the workpiece in such threat; that the off-beat relation means causes the feeding and the forming means to operate in off-beat relation relatively; and that the socket 114 and its associated parts receives the emerging leading increment of a workpiece immediately as it leaves the throat and guides it thereafter through its travel in response to the feed in a path coaxial with the path of the workpiece through the die throat while next adjacent increments are being plasticized; and that this guiding of theleading increment insures all the remaining increments being free of stresses and distortions.

It will further be observed that the feed means is arranged to travel in a path coaxial with the path through the throat, namely, the path traveled by the receiving means and guiding means 114.

Very important is it to observe that the parts are so constructed that the feed means 90 and the guiding means 114 travel a distance equal to a large multiple of the length of the dies and die throat whereby many increments of length of the workpiece may pass through the throat successively and with the travel of the guiding and receiving means 114 starting directly at the output end of the dies 44.

Now having described the means and method herein disclosed, I claim:

I claim as my invention:

1. Apparatus comprising a set of dies arranged radially and oppositely to provide a workpiece girdling and receiving throat, means for guiding the dies to move radially only while inhibiting other motion thereof, means for intermittently moving the dies simultaneously and oppositely and radially inwardly towards the axis of such throat and plasticizing the increment of the workpiece in such throat, means for intermittently feeding a workpiece axially through such throat, with the die moving means and the feeding means operating in otf-beat relation relatively and means for receiving the emerging increment of a workpiece immediately as it leaves the throat and guiding it thereafter through its travel, in response to the feed,

in a path coaxial with the path of the workpiece through the die throat, While next adjacent increments are being plasticized and means for guiding the workpiece increment receiving means to move in said path coaxial with the die throat, and constructed to permit the receiving means to travel directly to the output end of the dies and thus receive the very first increment of the workpiece as it leaves the dies and thereafter to retreat from the dies with that first increment held therein in said path.

2. A construction according to claim 1 wherein the feed means is arranged to travel in a path coaxial with the path through the throat and travelled by the guiding means for the emerging increment of the workpiece.

3. A construction according to claim 1 wherein the fed means and the guiding means travel a distance equal to a large multiple of the length of the dies and die throat whereby many increments of length of the workpiece may pass through the throat successively, with the travel of the guiding means starting directly, at the output end of the dies.

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